JP2001189356A - Measurement signal output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement signal output device which copes with light signals at a low level of power, prevents loss or imbalance from occurring in measured signals, and is easily handled or used. SOLUTION: An optoelectrical probe 15A and an optical input/output unit D are connected together with cables 37, 38, and 39, the optical input/output unit D and a power supply/measurement signal output unit E are connected detachably together with connectors 45 and 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring signal output for extracting an electric signal corresponding to a signal to be measured from an optical signal containing a polarization component corresponding to the voltage of the signal to be measured as a measuring signal and supplying it to a measuring instrument. Related to the device.

[0002]

2. Description of the Related Art As a conventional measurement signal output device, for example, an electro-optic crystal whose polarization plane is changed by an electric field is coupled to a portion where an internal signal of a measurement object such as an IC (hereinafter referred to as a signal to be measured) appears. An electro-optic probe having a built-in optical system for reproducing a signal to be measured based on the polarization state of light reflected from the electro-optic crystal and extracting an optical signal having a polarization state corresponding to the signal to be measured, and Some include a light receiving circuit for receiving light and extracting an electric signal corresponding to the polarization state.

This measurement signal output device is different from a conventional measurement system using an electric probe in that: 1) a ground line is not required when measuring a signal; Since the metal pin at the tip is electrically insulated from the oscilloscope side circuit system, it is possible to observe the waveform without substantially disturbing the state of the signal to be measured. 3) Broadband from optical pulse to gigahertz order It has the feature that measurement is possible.

[0004] An example of the configuration of an electro-optical probe used in the measurement signal output device will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a probe head made of an insulator, and a metal pin 1a that is in contact with a portion where a signal to be measured appears is fitted into the center of the probe head. Reference numeral 2 denotes an electro-optic element (electro-optic crystal) whose polarization plane is changed by an electric field. A reflection film 2a is provided on an end face on the metal pin 1a side, and is in contact with the metal pin 1a.

Reference numeral 4 denotes a half-wave plate, and reference numeral 5
Is a 波長 wavelength plate. Reference numerals 6 and 8 are polarization beam splitters. Reference numeral 7 denotes a Faraday element. Reference numeral 9 denotes a laser diode that emits laser light in response to a pulse signal (control signal) output from a measuring instrument body (not shown) such as an EOS oscilloscope. Reference numeral 10 denotes a collimating lens that converges the laser light from the laser diode 9 in one direction and converts the laser light into parallel light. A plate 4, a quarter-wave plate 5, polarizing beam splitters 6, 8, and a Faraday element 7 are arranged.

Reference numerals 11 and 13 denote condensing lenses for condensing the laser beams split by the polarizing beam splitters 6 and 8, respectively. Reference numerals 12 and 14 denote photodiodes as photoelectric conversion elements constituting a light receiving circuit described later, which convert the laser light condensed by the condensing lenses 11 and 13 into an electric signal and output the electric signal to the main body of the measuring instrument.

Reference numeral 15 denotes a probe body as an electro-optic probe. Reference numeral 17 denotes a quarter-wave plate, two polarization beam splitters 6 and 8, and a Faraday element 7.
, Which passes the light emitted from the laser diode 9 and separates the light reflected by the reflection film 2a.

Next, a configuration example of a conventional light receiving circuit used in a measurement signal output device will be described with reference to FIG. In the figure, reference numeral 100 denotes a bias power supply, reference numerals 12 and 14 denote photodiodes, reference numerals 102 and 105 denote resistors, and reference numeral 1.
Reference numerals 03 and 106 denote amplifiers, reference numeral 107 denotes a current monitor, reference numeral 108 denotes an A / D converter, and reference numeral 109 denotes resistors 109A to 109A.
Reference numeral 110 denotes a resistor, and reference numeral 111 denotes an A / D converter.

In this light receiving circuit, the currents generated by the photodiodes 12 and 14 biased by the bias power supply 100 are amplified by amplifiers 103 and 106, respectively, and the difference between the outputs of these amplifiers 103 and 106 is compared with the differential amplifier 1
09 to obtain a measurement signal by amplification. The output value of the differential amplifier 109 is A / D converted by an A / D converter 111. In addition, the photodiodes 12, 1
4 is monitored by a current monitor 107, and the current value is A / D converted by an A / D converter 108.

Next, the operation of the conventional device will be described. The laser diode 9 shown in FIG. 2 is driven by a pulse signal (control signal) and emits a pulsed laser beam A having a sampling period. This laser light A is
The light is converted into parallel light by the collimating lens 10, travels straight through the polarization beam splitter 8, the Faraday element 7, and the polarization beam splitter 6, and further passes through the quarter-wave plates 5 and 1 /
The light enters the electro-optical element 2 through the two-wavelength plate 4.

The incident laser light is reflected by the reflection film 2a formed on the end face of the electro-optical element 2 on the metal pin 1a side. Here, when the metal pin 1a is brought into contact with the measurement point, an electric field corresponding to the voltage applied to the metal pin 1a propagates to the electro-optical element 2, and the electro-optical element 2 is caused by the Pockels effect.
A phenomenon occurs in which the birefringence changes. As a result, when the laser light emitted from the laser diode 9 propagates through the electro-optical element 2, the polarization state of the light changes, and as a result,
The laser light reflected by the end face 2a of the electro-optical element 2 contains a polarization component corresponding to the voltage of the signal under measurement.

The laser light reflected by the end face 2a of the electro-optical element 2 passes through the half-wave plate 4 and the quarter-wave plate 5 again, and a part of the laser light (according to the voltage of the signal to be measured). Polarization component) is separated by the polarization beam splitter 6,
The light is condensed by the condenser lens 11 and is incident on the photodiode 12 constituting the light receiving circuit. The laser light transmitted through the polarization beam splitter 6 is separated by the polarization beam splitter 8, collected by the condenser lens 13, incident on the photodiode 14 shown in FIG. 3, and converted into an electric signal.

Here, the operation of the light receiving circuit will be described. When the birefringence of the electro-optical element 2 changes with the change in the voltage of the signal under measurement, a difference occurs between the outputs of the photodiodes 12 and 14. The light receiving circuit operates so as to output a measurement signal according to the signal under measurement by detecting the output difference.

That is, the photodiode 1 of the light receiving circuit
2 receives the laser beam from the polarizing beam splitter 6, the photodiode 12 generates a current corresponding to the intensity of the laser beam, and a voltage corresponding to the current appears at one end of the resistor 102 and is amplified by the amplifier 103. Is done. Similarly, the voltage corresponding to the current generated by the photodiode 14 is the resistance 1
05 and is amplified by the amplifier 106. The differential amplifier 109 outputs a measurement signal corresponding to the output difference between the amplifiers 103 and 106 to the measuring instrument main body side.

As described above, according to the conventional light receiving circuit,
The signals detected by the photodiodes 12 and 14 are amplified by amplifiers 103 and 106, respectively, and then the difference is obtained by a differential amplifier 109 to detect only the measurement signal.

The current monitored by the current monitor 107 is A / D converted by the A / D converter 108,
Together with the value of the measurement signal converted by the A / D converter 111, it is used for verification of operation of the photodiodes 12, 14 and calibration. Further, the electro-optical element 2
It is necessary to align the plane of polarization of the incident laser light with the crystal axis of. Therefore, the plane of polarization is adjusted by rotating the half-wave plate 4 and the quarter-wave plate 5.

[0017]

However, in such a conventional measurement signal output device, a conventional probe body 15 and a photodiode 12 for converting a laser beam output from the probe body 15 into a photocurrent are usually used. , 14,
And a current drive circuit for outputting a drive current to the laser diode 9 in the probe main body 15 based on a change in the monitor output of the photocurrent.
Since the connection is separable through such as, the transmission loss occurs at the connection portion, and the input / output error of the photocurrent and the drive current occurs due to imbalance of the electric resistance (contact resistance) of the connection portion, There has been a problem that a measurement signal with high measurement accuracy may not be output to a measuring instrument.

The present invention solves the above-mentioned problems, and
By treating the electro-optic probe, which is the probe body, and the light-receiving unit having the current drive circuit and the photodiode as inseparably coupled electrically and optically, low-level optical signals and signals to be measured are handled as signals. It is an object of the present invention to provide a measurement signal output device that can sufficiently prevent the occurrence of loss or imbalance of the measurement signal and can easily handle and use the measurement signal.

[0019]

To achieve the above object,
An electro-optic probe for receiving a light output from a light source and outputting a first light signal and a second light signal whose polarization has been changed in accordance with the voltage of the signal under measurement. And a first photoelectric conversion element connected in series between a first bias power supply and a second bias power supply for receiving the first optical signal and the second optical signal, respectively, and converting the optical signal into an electric signal And an output circuit for outputting an electric signal obtained at a connection point between the second photoelectric conversion element and the first photoelectric conversion element and the second photoelectric conversion element;
The light source is provided in the light input / output unit together with the second photoelectric conversion element and the output circuit, and receives a control voltage corresponding to a change in current flowing through the first photoelectric conversion element and the second photoelectric conversion element, and drives the light source. A current drive circuit for supplying a current, an amplifier connected to the optical input / output unit, for amplifying an electric signal obtained at the connection point and outputting the amplified signal to the measurement circuit side, and an electric circuit in the optical input / output unit. A power supply / measurement signal output unit having a power supply for supplying power, the electro-optic probe and the optical input / output unit being connected by a cable, and the optical input / output unit and the power supply / measurement signal output unit being connected by a connector Are connected so that they can be separated from each other.

According to a second aspect of the present invention, in the measurement signal output device, the power supply / measurement signal output unit is provided with an amplifier for amplifying and outputting an electric signal obtained at the connection point for a plurality of channels. It is.

According to a third aspect of the present invention, there is provided a measurement signal output device, wherein the electro-optic probe is connected to a light input / output unit which is different for each application.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. 1, reference numeral 15A denotes an electro-optic probe, which is configured by removing the phototransistors 12 and 14 from the electro-optic probe 15 shown in FIG. Reference numeral D denotes an optical input / output unit, in which photodiodes 21 and 22 are connected in series. A series circuit of these photodiodes 21 and 22 includes a current monitor 2 between a positive bias power supply 23 as a first bias power supply and a negative bias power supply 24 as a second bias power supply.
5 and 26, respectively. A signal output terminal 28 is connected to a connection point P between the photodiodes 21 and 22 via an (first-stage) amplifier 27.

The current monitors 25 and 26 monitor currents flowing through the photodiodes 21 and 22, respectively, and perform voltage conversion. These monitor values A and B are added to an adder 29.
To calculate A + B. Note that a change in the sum of the monitored currents corresponds to a change in the light emission amount of the laser diode 9. The operation output of the adder circuit 29 is input to the negative input terminal of the operational amplifier 30 via the resistor 31.
Further, an arbitrary reference voltage (control voltage) output from the reference voltage generator 32 constituting the drive current control circuit C is input to the positive input terminal of the operational amplifier 30. Therefore, this operational amplifier 30 is
And a control signal corresponding to the difference between the calculation output from the reference voltage generator and the reference voltage from the reference voltage generator 32. 33 is an operational amplifier 30
Connected between the output terminal and the negative input terminal of the
A resistor that determines the amplification factor together with 1. Note that the operational amplifier 30 and the reference voltage generator 32 constitute the drive current control circuit C together with the resistors 31 and 33.

A current drive circuit 34 is connected to the output side of the operational amplifier 30. This current drive circuit 34 is formed by connecting a current setting resistor 36 to the emitter of a transistor 35. This current drive circuit 34 is a transistor 3
Receiving the control signal from the operational amplifier 30 at the base of
That is, upon receiving a control signal corresponding to a change in monitor output from the current monitors 25 and 26, a drive current is supplied to the laser diode 9 as a light source in the electro-optic probe 15A via the coaxial cord 37 as a cable. Function. Note that this current drive circuit 34 is
Output a drive current for emitting light with either pulsed light or continuous light.

Although not shown, a monitor value (voltage value) of a current flowing through each of the photodiodes 21 and 22 is input to a subtraction circuit as necessary, and a deviation amount of the light balance is detected from a voltage difference obtained as a result of the subtraction. By doing so, it is possible to indirectly know the S / N deterioration amount. Therefore, the deviation of the light balance can be suppressed by correcting the deterioration amount, that is, by adjusting the polarization ratio of the optical signal received by each of the photodiodes 21 and 22 in the direction of suppressing the deterioration amount.

Further, between the electro-optic probe 15A and the light input / output unit D, laser light emitted through the polarizing beam splitters 6, 8 and the condenser lenses 11, 13 as shown in FIG. Optical fiber cables 38 and 39 as cables leading to the diodes 21 and 22 are fixedly attached.

Reference numeral E denotes a power supply / measurement signal output unit.
A signal input terminal 40 connected to the signal output terminal 28 of the optical input / output unit D, an amplifier 41 at the previous stage for amplifying the measurement signal received from the signal input / output terminal 40, a predetermined frequency in the measurement signal A filter 42 for removing a signal, an amplifier 43 at a subsequent stage, and a measurement signal output terminal 44 are provided. Here, the signal output terminal 28 and the signal input terminal 4
Reference numeral 0 denotes a coaxial connector 45 which is a high-frequency transmission connector.

The power supply / measurement signal output unit E includes a power supply 46 for supplying power to an electric circuit in the optical input / output unit D, a panel controller 47, a photodiode 21,
There is provided a balance monitor 48 for monitoring the shift amount of the light balance, which is a difference between the photocurrents 22, and a photocurrent monitor 49 for monitoring the light amount of the laser diode 9 with a value corresponding to the sum of the output currents of the photodiodes 21 and 22. ing. The power supply voltage, the balance monitor signal, and the photocurrent monitor signal can be exchanged between the optical input / output unit D and the power supply / measurement signal output unit E through each input / output contact constituting the multi-pole connector 50. I have. The power supply side circuit of the optical input / output unit D is connected to a slow start circuit 51 for gently rising the power supply voltage, thereby preventing the destruction of circuit elements due to the transient current.

Next, the operation will be described. First, power supply 4
After the electric power is supplied to each electric circuit from 6 and the metal pin 1a of the probe head 1 of the electro-optical probe 15A is brought into contact with the measurement point, the electric field generated at the metal pin 1a propagates to the electro-optical element 2 as described above. I do. On the other hand, the laser light from the laser diode 9 propagates to the electro-optical element 2, and the laser light reflected at the end face includes a deflection component corresponding to the voltage of the signal under measurement, and includes the half-wave plates 4 and 1 The light is separated and output from the deflecting beam splitters 6 and 8 through the 波長 wavelength plate 5.

Each of the separated laser beams exits the electro-optic probe 15A and is connected to the photodiodes 21 and 22 of the optical input / output unit D by the respective optical fiber cables 38 and.
Irradiated through 39, it is converted into an electric signal according to the intensity of the laser beam. Photodiodes 21 and 22
Occurs at the connection point P, and the amplifier 27, the coaxial connector 45, the amplifier 41, the filter 42, and the amplifier 4
The signal is output to a measuring instrument such as an oscilloscope or a spectrum analyzer through the measuring signal output terminal 3 and the measurement signal output terminal 44.

When the output of the laser diode 9 fluctuates, the current flowing through the photodiodes 21 and 22 changes even if the signal to be measured remains constant. Therefore, the added value of the voltage obtained through each of the current monitors 25 and 26 also changes, and this added value is compared with the voltage reference value from the reference voltage generator 32 by the operational amplifier 30, and according to the calculation result, A control signal for stabilizing the light of the laser diode 9 is input to the current drive circuit 34. Therefore, the optical output of the laser diode 9 can be stabilized irrespective of the change in the current flowing through the photodiodes 21 and 22, and the detection sensitivity of the signal under measurement can be kept constant.

As described above, by receiving two optical signals having deflection characteristics according to the voltage of the signal to be measured, the output light of the laser diode 9 can be adjusted according to the fluctuation of these signals. The fluctuation can be prevented from appearing as an error in the measurement signal, and the received optical signal can be converted into an electric signal with high accuracy, whereby the measurement accuracy of the measuring instrument can be improved.

According to the present invention, since the level of the optical signal and the electrical signal handled between the electro-optical probe 15A and the optical input / output unit D are relatively small and slightly change, the level of the optical signal and the electrical signal is changed. The transmission and reception can be performed using the optical fiber cables 38 and 39 and the coaxial cable 37 fixedly connected between the electro-optic probe 15A and the optical input / output unit D without using a connector. By doing so, loss of the optical signal or the electric signal and leakage to the outside can be reliably prevented. Further, if the optical fiber cables 38 and 39 and the coaxial cable 37 are shortened, the loss can be further reduced and the detection sensitivity of the signal under measurement can be further improved.

The electro-optic probe 15A is used properly depending on the application. In this case as well, the electro-optic probe 15A is integrated with the optical input / output unit D and handled. On the other hand, the optical input / output unit D and the power supply / measurement signal output unit E
A coaxial connector 45 for outputting a measurement signal and a multi-pole connector 50 for inputting / outputting a power supply voltage, a balance monitor signal, and a photocurrent monitor signal are detachably connected to each other so that they can be arbitrarily attached and detached. It has become. Therefore, the electro-optic probe 15A is used depending on the application.
Is connected to the power supply / measurement signal output unit E together with the optical input / output unit D integrated therewith.
Even when the power supply / measurement signal output unit E is provided with a plurality of measurement signal transmission systems, the electro-optic probe 15A is integrated with the optical input / output unit D via the predetermined coaxial connector 45. It is detachably connected so as to be connected to the amplifiers 41 and 43 and the filter 42 of one of the channels.

The type of the electro-optic probe 15A is, for example, sensitivity 1, frequency characteristic 10 MHz to 1 GHz.
Standard type, sensitivity 3, frequency characteristic 50MHz ~ 1G
There is a high-sensitivity type of Hz, and an optical input / output unit having performance and function corresponding to each type is integrally connected to these types.

The electro-optical element 2 of the probe head 1
Instead of contacting the metal pin 1a with the metal pin 1a,
By abutting the socket for detachably supporting (replacement) a, replacement of only the metal pin 1a can be performed quickly and easily.

[0037]

As described above, according to the present invention, the electro-optical probe and the optical input / output unit are connected by the cable, and the optical input / output unit and the power supply / measurement signal output unit can be separated by the connector. The connection prevents loss or imbalance of low-level optical signals and signals under measurement as signals to be handled, and facilitates handling and use by connecting connectors at relatively large signal levels. The effect is obtained.

Further, according to the present invention, the power supply / measurement signal output unit is provided with an amplifier for amplifying and outputting an electric signal obtained at the connection point for a plurality of channels. A plurality of sets of electro-optic probes can be connected to the power supply / measurement signal output unit together with the optical input / output unit, and the advantage that the measurement work for each application can be quickly switched is obtained. In addition, since the electro-optic probe is connected to a different optical input / output unit for each application, it can be detachably attached to the power supply / measurement signal output unit as an integrated electro-optic probe and optical input / output unit that differs for each application Connection becomes possible, and its use and handling become easy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a measurement signal output device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram conceptually showing an electro-optic probe in a conventional measurement signal output device.

FIG. 3 is a block diagram showing a light receiving circuit in a conventional measurement signal output device.

[Explanation of symbols]

 15A Electro-optic probe 21 Photodiode (first photoelectric conversion element) 22 Photodiode (second photoelectric conversion element) 23 Positive bias power supply (first bias power supply) 24 Negative bias power supply (second bias power supply) 27, 41, 43 Amplifier (output circuit) 34 Current drive circuit 37 Coaxial cord (cable) 38, 39 Optical fiber cable (cable) 45 Coaxial connector (connector) 46 Power supply 50 Multipolar connector (connector) D Optical input / output unit E Power supply / measurement signal output unit P connection point

Continued on the front page (72) Inventor Junichi Banjo 4-19-7 Kamata, Ota-ku, Tokyo Inside Ando Electric Co., Ltd. (72) Inventor Jun Kikuchi 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric (72) Inventor Sanjay Gupta 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric Corporation (72) Inventor Mitsuru Shinagawa 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Within Telephone Co., Ltd. (72) Inventor Chisato Hashimoto 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Tadao Nagatsuma 2-3-1, Otemachi, Chiyoda-ku, Tokyo Sun Within the Telegraph and Telephone Co., Ltd. BA06 CA05 DD03 DD08 DE14 5J092 AA01 AA56 CA00 CA36 FA20 HA02 HA19 HA25 HA44 KA00 KA01 KA02 KA12 KA26 KA28 KA34 KA41 KA61 SA13 TA01 UL02

Claims (3)

[Claims] An electro-optic probe for receiving a light output from a light source and outputting a first light signal and a second light signal whose polarization has been changed in accordance with the voltage of a signal under measurement; a first bias power supply; A first photoelectric conversion element and a second photoelectric conversion element, which are connected in series between the second bias power supply and receive the first optical signal and the second optical signal, respectively, and convert the optical signals into electric signals; An output circuit for outputting an electric signal obtained at a connection point between the first photoelectric conversion element and the second photoelectric conversion element; and an optical circuit together with the first photoelectric conversion element, the second photoelectric conversion element, and the output circuit. A current driving circuit provided in the input / output unit and receiving a control voltage according to a change in current flowing through the first photoelectric conversion element and the second photoelectric conversion element and supplying a driving current to the light source; Connected to the input / output unit, Amplifier that outputs to the measuring circuit side amplifies the electrical signal obtained in connection point,
And a power supply / measurement signal output unit having a power supply for supplying power to an electric circuit in the optical input / output unit, wherein the electro-optical probe and the optical input / output unit are connected by a cable, And a power supply / measurement signal output unit are connected to be separable by a connector. 2. The measurement signal according to claim 1, wherein the power supply / measurement signal output unit includes amplifiers for amplifying and outputting an electric signal obtained at the connection point for a plurality of channels. Output device. 3. The measurement signal output device according to claim 1, wherein the electro-optic probe is connected to a different optical input / output unit for each application.